Pappardelle with legumes and grilled lemon

Ingredients

• 1 large red onion
• 1 lemon
• 150 g garden peas in their pods
• 300 g broad beans in their pods
• 150 g crème fraîche
• 1 tbsp. lemon juice
• 300 g pappardelle
• ½ tbsp. lemon zest
• olive oil